Companies engaged in the lumber and pulp and paper business for economical reasons are constantly striving to develop new methods and improve existing methods of harvesting trees from timber stands.
At present, using current mechanical harvesting methods, it is usually uneconomical to harvest trees measuring four to nine inches in butt diameter that typically grow in relatively flat sometimes marshy areas located in Northern regions. This size of tree may be mixed in with larger diameter trees. The only feasible method of cutting such trees in these areas is by means of hand operated chain saws. However, this method is labour intensive, which is undesirable for the following reasons. First, on average, labour time per tree is high because it normally takes one man using a chain saw at least one minute to harvest an eight inch diameter tree. Moreover, working conditions for the chain saw operator are often uncomfortable because there is often excessive cold in the winter time, there are usually excessive biting insects, heat, and humidity in the summer time, and the chain saw operator experiences back fatigue because bending over is required to cut the trees, and the chain saw operator over a long period of time may develop "white hands" which is a term for permanent loss of feeling in the hands and is believed to be caused by a workman gripping a vibrating object, such as a chain saw, for a number of hours each day over a prolonged period of time.
Further, it is necessary to pay much higher rates to piece workers in small trees for equal wood volume produced. On day rates, less wood volume is produced for a day's pay. This system of compensation favours the cutting of larger trees, and hence the smaller trees are avoided because they are unprofitable to cut.
Finally, there is an increasing shortage of good manpower in the "bush" because most people now prefer to work in urban areas. As a result, many potentially useful stands of timber including trees with diameters measuring four to nine inches, and often larger diameters, are not being harvested.
In Canadian Pat. No. 1,029,283, granted April 11, 1978, to Prince Albert Pulpwood Ltd. and identifying two of the inventors (Bruce Hyde and Wayne Tyndall) named in connection with the present invention, there is disclosed and claimed a low manual labour method and apparatus whereby trees mainly measuring from about four inches to nine inches in butt diameter, but including trees with butt diameters smaller than four inches or larger than nine inches, can be continuously and economically harvested by moving a tree cutting means mounted on a moving means such as a powered wagon through trees standing along the edge of a stand of such trees. The trees are harvested by cutting a swath of such trees using the apparatus at a velocity and in a manner whereby the cut trees topple in the swath path in a substantially parallel pattern.
While the invention disclosed and claimed in Canadian Pat. No. 1,029,283 enables trees to be harvested at unprecedented rates, it has been found that non-vertical trees, high wind conditions and high cutting speeds can be adverse factors and it would be advantageous if it would be possible to control the movement of the toppling trees after they have been cut.